The present invention relates generally to the melting of solid scrap metal in a molten melting media and particularly to a method and apparatus for more effective melting of scrap metal and ingestion of any skim material associated with the media and scrap.
Interest remains high in reclaiming (recycling) metal scrap, particularly lightweight metal scrap such as aluminum. The collection and remelting of solid scrap material are more efficient than the production of new metal, since such production involves mining the original ores and processing the same to extract the metal therefrom. A particularly useful process in regard to remelting metal scrap is a continuous remelt process in which superheated molten metal is circulated from a heating bay to a scrap charging bay by a pump located in the charging bay. Scrap metal is fed to the charging bay from a position over the rotor of the pump. The pump rotor creates a vortex of the melting media in the charging bay that serves to submerge and ingest the scrap in the media. Without such an ingestion process, metal scrap having a large surface to weight ratio tends to float on top of the melting media. Continuous melting processes using pump ingestion are disclosed in U.S. Pat. Nos. 3,997,336 and 4,128,415 to Van Linden et al.
Also known is a process described in U.S. Pat. No. 3,272,619 to Sweeney et al in which a pump is used to direct molten metal from a furnace (containing the metal) and to a hopper structure. In the hopper, the flow of metal is tangential along the side wall thereof, such that the metal forms a vortex as it cascades downwardly through the hopper and out a bottom outlet of the hopper. The hopper and pump are raised and lowered by a reversing motor and supporting frame and linkage to maintain appropriate submersion of the pump and hopper when the height of the molten metal fluctuates. Such fluctuation occurs when the scrap material is fed to the hopper and when metal is removed from the furnace. In addition, the text of the patent indicates that the intensity of the vortex is increased when the hopper is in a raised position, such that solids in the media are more rapidly submerged for flow through the bottom outlet of the hopper.